Rotary furnace drive



1945- R. E. BUCKHOLDT ROTARY FURNACE DRIVE Filed Dec. 22, 1942 2 Sheets-Sheet l Qwuwn/Lom ROBERT E. BUCKHOLDT 1945- R. E. BUCKHOLDT ROTARY FURNACE DRIVE *iled Dec. 22, 1942 2 Sheets-Sheet 2 awuc wboo ROBERT E. BUCKHOLDT Shauna;

Patented Feb. 13, 19 45 no'rlmr ruaunca muvn Robert E. Buckholdt, Salem, Ohio, minorto The Salem Engineering Ohio, a proprietorsliip Application December 22. 1942, Serial No. 469,804

8 Claims. (Cl. 198-209) This invention relates to rotary hearth furnaces and more"- particularly to improved arrangements and devices for driving the movable or rotary 'hearths thereof.

The operation and maintenance of the hearth driving mechanisms in furnaces of the rotary hearth type has heretofore presented serious problems, particularly in furnaces of the larger sizes, due to warpage and distortion of the frame supporting the hearth and consequently of the rack gear, or other driven member carried by the hearth frame. While provisions have been made to minimize distortion of the hearth frame relative to the fixed parts of the complete furnace, such as allowing the hearth itself to expand and warp independently of its supporting frame and by providing guiding devices to maintain the alignment of the movable and fixed parts of the furnace, some distortion of the parts is unavoidable and in many instances operates to excessively load the driving mechanism and even to render the driving mechanism inoperative. It is the primary object of the present invention to provide an improved driving connection for the hearth of a rotary hearth furnace which connection is encientl-y operative regardless of the presence of distortion in either the hearth or in the structural frame supporting the hearth. The distortion in the hearth or hearth frame may be either in a horizontal plane thereby making the hearth or hearth frame slightly out of round or in a vertical direction thereby causing the hearth and'hearth frame to assume a somewhat wavy condition.

The apparatus of the invention compensates for both these conditions but is, nevertheless, simple in design and subject to a minimum of wear.

In one embodiment of the invention there is secured to the hearth frame, in accordance with usual practice, a rack which is arranged to be meshed with a driven. pinion but instead of sup- :porting the pinion for rotation about a fixed axis as has heretofore been the .practice the pinion is.

mounted on a movable or supporting member which is maintained in proper position relative to the rack at all times so that the circular pitch line of the pinion will be at all times maintained substantially tangent to the pitch lin of the rack. Thisprovides for distortion of the hearth frame in a vertical direction if the rack and pinion are horizontally mounted and for distortion in a horizontal plane it the rack and pinion are vertically mounted. Distortions'normal to theabove are compensated for by so constructing the mechanism that the rack and pinion may have relative Company, Salem,

movement in a direction transverse of the principal axis or line of movement of the rack.

The above and other'obiccts and advantages of the invention will become apparent upon a consideration of the following detailed specification and the accompanying drawings wherein there is specifically disclosed a preferred embodiment of the invention.

In the drawings:

Figure 1 is a-fragmentary horizontal section, broken away in part, of a rotary hearth furnace constructed in accordance with the principles of the invention;

Fi ure 2 is a vertical section of the furnace of Figure 1, the view being taken along the line II-II of Figure 1;

Figure 3 is a side elevation of a portion of the hearth driving assembly of the invention;

Figure .4 is a plan view of the apparatus of Figure 3 and Figure 5 is an end elevation of the apparatus of Figure 3.

The furnace chosen for illustration purposes includes, in accordance with usual practice,,inner and outer concentric groups it and ii, respectively, of vertically extending buckstays which are tied together at their top ends by the horizontal members it. The buckstays it and it retain the concentric inner and outer walls 63 and it, re-

spectively, of the furnace, which walls are supthe wheels or rollers 26 which are journaled-in members attached to the frame and which are arranged to travel on the circular track rails 2i. Means, such as shown at til, 5i56 in U. S. Patent No. 2,296,791 Keener et al., may be provided to maintain th concentric alignment of thehearth 'and'hearth frame with respect to the fixed walls of the furnace but it should be understood that insofar as the present invention is concerned. any operative arrangement for rotatably supportin .and guiding the hearth may be utilized.

' Referring now to Figure 3 it will be observed that depending from the outer edge ,of the hearth frame i9 isi'a circular box-like structure 22 formed,

principally, by concentrically spaced channelmembers. To the lower flanges of these channel members is secured a plate member 23 which pro- -.vides a radially outward extending continuous projection 24. Also secured to the member 22 but positioned below the plate 23 is a rack 25 which is also continuous-extending completely around the hearth frame.

Journaled in spaced pillow blocks 25 which are rigidly supported on a suitable base 21 is a shaft 28 which is arranged to be rotated by a motor 23 through a speed reducing unit 38. mounted on shaft 28 is a cradle 3| comprising a rigid frame in which is journaled a shaft 32 positioned substantially parallel to the shaft 28. A spur gear 33 keyed or otherwise rigidly secured to the shaft 28 meshes with a spur gear 34 keyed or otherwise rigidly secured to the shaft 32 so that rotation of the shaft 28 results in corresponding rotation of the shaft 32.

Rigidly secured to the cradle 3| and preferably forming an integral part thereof, as shown, is an upwardly extending member 35 in the upper portion of which is journaled the integral shaft of a roller 36. It will be understood that suitable anti-friction bearings may be employed in journaling the various shafts of the assembly.

A pinion 31 mounted on the shaft 32 and keyed or otherwise rigidly secured thereto is arranged to mesh with the gear teeth of the rack 25 and to insure that the pitch line of the teeth and the rack 25 is always substantially tangent to the pitch circle of the pinion 31 the roller 36 is arranged to engage the upper flat surface of the projection 24 of the plate 23, as shown in Figure 3. It should be apparent that with this arrangement any warpage in a vertical direction of the hearth frame and consequently of the rack 25 and of the plate 23 will not affect the driving connection between the pinion 31 and the rack 25 since the roller 36 acting through the arm 35 will rock the cradle 3| as required to maintain the proper interengagement of the rack and pinion.

The horizontal disposition of the axis of the roller 36 and of the top flat surface of the projection 24 enables the projection 24 to move laterally with respect to the roller 36 while still retaining the mode of operation above described. Also the rack 25 and pinion 31 have suflicient width and are otherwise so constructed that, within limits, the position of the rack may vary axially of the pinion without affecting the operation of the driving connection. Thus the driving arrangement of the invention provides for distortion in the hearth frame and rack in a horizontal direction and the connection remains operative even though considerable distortion takes place.

It should now be apparent that the present invention provides an improved driving arrangement for a rotary hearth furnace which accomplishes the objects and advantages initially set out. Through the use of practical apparatus it is possible to provide and maintain an efficient driving connection for the rotary hearth of the furnace regardless of the presence of horizontal or vertical distortion in the hearth or in the hearth supporting frame. Moreover such distortion cannot operate to improperly load the driving force transmitting members which condition heretofore has resulted in excessive wear of the parts and in stoppage of the furnace in many cases.

The above specifically disclosed embodiment of the invention should be considered as illustrative only as obviously many changes may be made therein without departing from the spirit or scope of the invention. The invention is therefore not to be limited except insofar as required by the Rotatably prior state of the art and the scope of the ap pended claims.

What I claim is:

1. Hearth driving apparatus for a rotary hearth furnace having a rotatable circular frame for the support of the hearth comprising in combination an annular rack gear secured to said frame and having downwardly projecting gear teeth lying in a substantially horizontal plane, a flange secured to said frame and presenting an annular substantially flat horizontally disposed upp r bearing surface, a drive shaft, a cradle swivably mounted on said drive shaft, a pinion gear journaled on said cradle and adapted to mesh with said rack gear, meansv establishing a driving connection between said shaft and said pinion gear, and a roller rotatably carried by said cradle for rotation about a generally horizontal axis disposed radially with respect to said hearth, said roller engaging said upper bearing surface of said flange, said flange and roller being so proportioned that the flange may move axially with respect to said roller while said engagement is maintained whereby the operation and efliciency of said apparatus is unimpaired by distortion of said frame in either a horizontal or a vertical direction.

2. Hearth driving apparatus for a rotary hearth furnace having a rotatably mounted frame for the support of the hearth comprising in combination an annular rack gear secured to said frame and having downwardly projecting gear teeth lying in a substantially horizontal plane, means providing an annular shoulder rigidly secured to said frame, a drive shaft, a cradle swivably mounted on said drive shaft, a pinion gear journaled on said cradle and adapted to mesh with said rack gear, means establishing a driving connection between said shaft and said pinion gear, and a roller rotatably carried by said cradle for rotation about a generally horizontal axis disposed radially with respect to said hearth, said roller resting on said shoulder to maintain said pinion gear in proper mesh with said rack gear.

3. Hearth driving apparatus for a rotary hearth furnace having a rotatably mounted frame for the support of the hearth comprising in combination a circular rack gear secured to said frame, a drive shaft, a cradle swivably mounted on said drive shaft, a pinion gear journaled on said cradle and adapted to mesh with said rack gear, means establishing a driving connection between said shaft and said pinion gear, a circular guiding surface on said frame, and a roller carried by said cradle and engaging said surface to maintain said pinion gear in proper mesh with said rack gear.

4. Hearth driving apparatus for a rotary hearth furnace having a rotatably mounted frame for the support of the hearth comprising in combination a box-like circular beam rigidly secured to the lower side of said frame, an annular plate rigidly secured to the lower face of said beam and having an annular radially projecting portion to provide an upwardly disposed guiding surface, an annular rack gear underlying said plate and also rigidly secured to said beam, a drive shaft journaled for rotation about a fixed axis, a cradle journaled on said drive shaft for pivotal movement about said axis, a pinion gear journaled on said cradle and adapted to mesh with said rack gear, means establishing a driving connection between said shaft and pinion gear, and a roller carried by said cradle and engaging said surface to maintain said pinion gear in proper mesh with said rack gear.

5. Hearth driving apparatus for arotary hearth furnace having a rotatably mounted frame for the support of the hearth comprising in combination a circular box-like beam secured to said frame, a circular plate rigidly secured to said beam and having an integral flange providing a circular guiding surface, a circular rack gear secured to said plate opposite said beam, a drive shaft joumaled for rotation-about a fixed axis, a cradle journaled on said drive shaftfor pivotal movement about said axis, a pinion gear journaled on said cradle and adapted to mesh with said rack gear, means establishing a driving connection between said shaft and said pinion gear, and a follower carried by said cradle and engaging said surface to maintain said pinion gear in proper mesh with said rack gear.

6. Hearth driving apparatus for a rotary hearth furnace having a rotatably mounted frame for the support of the hearth comprising in combination a circular rack gear secured to said frame, a drive shaft Journaled for rotation about cent portion of said rack gear whereby said pinion gear is maintained in proper mesh with said rack gear.

7. Hearth driving apparatus for a rotary hearth furnace having a rotatably mounted frame for the support of the hearth comprising in combination a circular rack gear secured to said frame, a drive shaft journaled for rotation about a fixed axis, a cradle journaled on said shaft for pivotal movement about said axis, said cradle comprising a rigid unitary member having a pinion gear journaled therein, means establishing a driving connection between said shaft and pinion gear, means carried with said frame to provide a circular guiding surface, an integral arm on said cradle, and a roller journaled in said arm and engaging said surface to maintain said pinion gear in proper mesh with said rack gear.

8. Hearth driving apparatus for a rotary hearth furnace having a rotatably mounted frame for the support of the hearth comprising in combination a circular rack gear secured to said frame, a drive shaft journaled for rotation about a fixed axis spaced from and extending substantially across the face of said gear, a cradle journaled for rotation about said axis, a pinion gear joumaled on said cradle and adapted to mesh with said rack gear, said axis and the axis of rotation of said pinion gear being spaced circumferentially about said rack gear, means establishing a driving connection between said shaft and said pinion gear, and means to pivot said cradle about said first mentioned axis whereby said pinion gear is maintained in proper mesh with said rack gear.

ROBERT E. BUCKHOLDT. 

